1. Field of the Invention
The present invention relates to an optical displacement-measuring apparatus.
2. Description of the Related Art
The use of an x-y scale has been known in the art to optically detect a two-axial displacement along x- and y-axes. A sensor head for reading the displacement of the x-y scale includes two photosensitive devices mounted thereon to provide displacement signals along x- and y-axes
When two photosensitive devices are mounted on a substrate, the x-y squareness depends on the installation accuracy. Therefore, it is difficult to achieve a high precise x-y squareness. In addition, since the two photosensitive devices are mounted at individual locations on the substrate, the sensor head can not be downsized. In general, the substrate for use in mounting the photosensitive devices thereon employs a rigid, flat substrate such as a glass substrate. The x-y scale has a scale surface that is not always flat but often spherical and cylindrical. Accordingly, a structure that mounts the photosensitive devices on a rigid substrate can not be applied flexibly to x-y scales that have various scale surfaces.
The present invention has been made in consideration of the above situation and accordingly has an object to provide an optical displacement-measuring apparatus that includes photosensitive device arrays integrated at an excellent squareness for detecting two-axial displacements.
The present invention has another object to provide an optical displacement-measuring apparatus with a sensor head that includes photosensitive device arrays integrated small for detecting two-axial displacements.
The present invention has a further object to provide an optical displacement-measuring apparatus with a sensor head that can be flexibly applied to various scale surfaces.
The present invention provides an optical displacement-measuring apparatus having a scale on which optical gratings formed along a first axis and a second axis, and a sensor head arranged opposite to said scale and relatively movable along said first and second axes. The sensor head has a photosensitive unit for optically detecting a relative movement to provide a displacement signal. The photosensitive unit has a substrate, and a first and second photosensitive device arrays formed with a first semiconductor film deposited on said substrate and arrayed along said first and second axes at a certain pitch for providing displacement signals corresponding to the displacement along said first and second axes, respectively.
The apparatus also has a scale on which optical gratings formed along a first axis and a second axis crossing the first axis, and a sensor head arranged opposite to the scale and relatively movable along the first and second axes. The sensor head includes a photosensitive unit for optically detecting a relative movement to provide a displacement signal. The photosensitive unit has a substrate, a first photosensitive device array formed with a first semiconductor film deposited on the substrate and arrayed along the first axis at a certain pitch for providing a displacement signal corresponding to a displacement along the first axis, an insulator layer covering the first photosensitive device array, and a second photosensitive device array formed with a second semiconductor film deposited on the insulator layer and arrayed along the second axis at a certain pitch for providing a displacement signal corresponding to a displacement along the second axis.
According to the present invention, the photosensitive unit for measuring two-axial displacements is configured as a structure of two photosensitive device arrays formed through deposition of and lithography to semiconductor films. Therefore, the two-axial photosensitive device arrays have an excellent squareness, resulting in a small, high-performance, optical displacement-measuring apparatus.
In the present invention, the substrate of the photosensitive unit may be made of a transparent substrate having a front surface on which the first and second photosensitive arrays are formed and the reverse surface serving as light incident surface. The substrate may be made of a flexible resinous substrate, thereby flexibly corresponding to scale surfaces having two-dimensional optical gratings even if the surfaces are curved.
The present invention also provides an optical displacement-measuring apparatus, which has a scale having optical gratings formed thereon. The apparatus also has a sensor head arranged opposite and relatively movable to the scale. The sensor head includes a photosensitive unit for optically detecting a relative movement to provide a displacement signal. The photosensitive unit has a substrate, and a photosensitive device array formed with a semiconductor film deposited on the substrate and patterned. At least one of the scale and the photosensitive unit is formed using a flexible resinous substrate.
According to the present invention, at least one of the scale and the photosensitive unit is formed with a flexible resinous substrate, thereby flexibly responding to any cases where the scale has one- or two-dimensional optical gratings and the scale surface is cylindrical, spherical or free curved.
Specifically in the present invention, the photosensitive device array preferably includes a flexible resinous substrate, and a plurality of photosensitive devices formed with a semiconductor film deposited on the flexible resinous substrate for providing displacement signals with different phases.
When the scale has two-dimensional optical gratings, the photosensitive unit may include first and second photosensitive device arrays formed at different locations on the substrate corresponding to the two-dimensional optical gratings. Alternatively, the photosensitive unit may include first and second photosensitive device arrays stacked at the same location on the substrate sandwiching an insulator layer therebetween corresponding to the two-dimensional optical agratings.
In the present invention, an electroluminescence device may be used as a surface luminous light source in the sensor head for illuminating the scale.
Other features and advantages of the invention will be apparent from the following description of the preferred embodiments thereof.